Tire having cured photopolymer air barrier coating

Abstract

A tire has on its inner surface an elastomeric air barrier coating, which is formed by photocuring a compositioin comprising: (a) an end capped prepolymer (MW 2500-10,000) formed by reacting a polyester diol (MW750-1500) with a diisocyanate, and reacting the resulting diisocyanate terminated prepolymer with an end group forming compound; (b) one or more monofunctional addition polymerizable monomers; and (c) a photoinitiator or mixture thereof. In preferred embodiments, the polyester diol is hydroxyl terminated ethylene adipate, the diisocyanate is TDI, and the end group forming compound is 2-hydroxyethyl methacrylane (HEMA). The monofunctional monomer may be or include N-vinyl-pyrrolidone (NVP). The air barrier coating has high elongation, low modulus, good heat aging resistance and good adhesion to the tire in addition to low oxygen permeability.

What is claimed is: 
     
       1. A composite elastomer article comprising: (a) an elastomer having low air permeability, high elongation and low 100 percent modulus, said elastomer being in the form of a sheet or film, said elastomer being a reaction product formed by radiation curing of a composition comprising: (1) from about 60 to about 90 parts by weight of an end capped prepolymer having a molecular weight in the range of about 2,500 to about 10,000, said prepolymer being a reaction product of (i) a polyester diol having a molecular weight in the range of about 700 to about 1500, and formed by reaction of an alkanediol containing from 2 to about 6 carbon atoms with an aliphatic dicarboxylic acid containing from 2 to about 10 carbon atoms; (ii) an organic diisocyanate and (iii) an addition polymerizable end group compound having one carbon-to-carbon double bond and one hydroxyl group per molecule, wherein the mole ratio of --NCO groups is said diisocyanate to --OH groups in said diol is from about 1.12 to about 1.4, and wherein said end capped prepolymer is prepared by first reacting said polyester diol with said diisocyanate to form a diisocyanate terminated polyester urethane prepolymer comprising alternating units of said polyester diol and said diisocyanate and containing from about 2 to about 8 polyester diol units per mole, and then reacting said diisocyanate terminated prepolymer with said end group compound; and   (2) from about 40 to about 10 parts by weight of a monofunctional addition polymerizable reactive diluent monomer or mixture thereof;     (b) said sheet or film being adhered to a polymeric substrate.   
     
     
       2. A cured photopolymer according to claim 1 in which said polymeric substrate is rubber. 
     
     
       3. A process for preparing a composite article comprising an elastomer coating on a rubber substrate, said process comprising: (a) treating a surface of said rubber substrate in order to improve adhesion of said cured elastomer;   (b) applying to the treated surface an elastomer-forming radiation curable composition comprising: (1) from about 60 to about 90 parts by weight of an end capped prepolymer having a molecular weight in the range of about 2,500 to about 10,000, said prepolymer being a reaction product of (i) a polyester diol having a molecular weight in the range of about 700 to about 1500, and formed by reaction of an alkanediol containing from 2 to about 6 carbon atoms with an aliphatic dicarboxylic acid containing from 2 to about 10 carbon atoms; (ii) an organic diisocyanate and (iii) an addition polymerizable end group compound having one carbon-to-carbon double bond and one hydroxyl group per molecule, wherein the mole ratio of --NCO groups is said diisocyanate to --OH groups in said diol is from about 1.12 to about 1.4, and wherein said end capped prepolymer is prepared by first reacting said polyester diol with said diisocyanate to form a diisocyanate terminated polyester urethane prepolymer comprising alternating units of said polyester diol and said diisocyanate and containing from about 2 to about 8 polyester diol units per mole, and then reacting said diisocyanate terminated prepolymer with said end group compound; and   (2) from about 40 to about 10 parts by weight of a monofunctional addition polymerizable reactive diluent monomer or mixture thereof; and     (c) radiation curing said radiation curable composition, whereby a cured elastomer coating having low air permeability is formed.   
     
     
       4. A process according to claim 3 in which said radiation curable composition is a photocurable composition which is cured by means of actinic light. 
     
     
       5. A process according to claim 3 in which said radiation curable composition is applied to a cured rubber substrate. 
     
     
       6. A process according to claim 5 in which said treating a surface comprises priming said surface and applying an adhesive thereto, said adhesive being a material which is capable of bonding both to the substrate and to subsequently applied radiation curable composition, and in which said radiation curable composition contains an adhesion improving addition polymerizable reactive monomer. 
     
     
       7. A process according to claim 5 in which said cured rubber substrate is a cured rubber tire and said radiation curable composition is applied to the inner surface thereof. 
     
     
       8. A process according to claim 3 in which said radiation curable composition is applied to an uncured rubber substrate. 
     
     
       9. A process according to claim 8 in which said uncured rubber substrate is sulfur curable and said treating a surface comprises applying a primer to said surface and irradiating said surface. 
     
     
       10. A process according to claim 8 in which said uncured rubber substrate is peroxide curable and said treating a surface comprises applying a radiation curable surface treatment composition containing an addition polymerizable reactive monomer or mixture thereof to said surface and irradiating said surface. 
     
     
       11. A process according to claim 8 in which said uncured rubber substrate is a green tire and said radiation curable composition is applied to the inner surface thereof. 
     
     
       12. A process according to claim 11 including the further step of curing said green tire by heat and pressure after said radiation curable composition has been cured. 
     
     
       13. A process for preparing a composite article comprising an elastomer coating on a cured rubber substrate, said process comprising: (a) treating a surface of an uncured rubber substrate in order to improve adhesion of said cured elastomer coating to said substrate when cured;   (b) applying to the treated surface of said uncured rubber substrate an elastomer-forming photocurable composition, said photocurable composition comprising a photoinitiator, a polyurethane having carbon-to-carbon double bond unsaturation, and a monofunctional addition polymerizable reactive diluent monomer;   (c) photocuring said photocurable composition with actinic light to form said elastomer coating; and   (d) curing said rubber substrate.   
     
     
       14. A composite elastomer article comprising: (a) a cured rubber substrate and   (b) an elastomeric coating of low air permeability bonded to at least one surface of said rubber substrate, said coating being a radiation cured reaction product of an elastomer-forming photocurable composition comprising: (1) from about 60 to about 90 parts by weight of an end capped prepolymer having a molecular weight in the range of about 2,500 to about 10,000, said prepolymer being a reaction product of (i) a polyester diol having a molecular weight in the range of about 700 to about 1500, and formed by reaction of an alkanediol containing from 2 to about 6 carbon atoms with an aliphatic dicarboxylic acid containing from 2 to about 10 carbon atoms; (ii) an organic diisocyanate and (iii) an addition polymerizable end group compound having one carbon-to-carbon double bond and one hydroxyl group per molecule, wherein the mole ratio of --NCO groups is said diisocyanate to --OH groups in said diol is from about 1.12 to about 1.4, and wherein said end capped prepolymer is prepared by first reacting said polyester diol with said diisocyanate to form a diisocyanate terminated polyester urethane prepolymer comprising alternating units of said polyester diol and said diisocyanate and containing from about 2 to about 8 polyester diol units per mole, and then reacting said diisocyanate terminated prepolymer with said end group compound; and   (2) from about 40 to about 10 parts by weight of a monofunctional addition polymerizable reactive diluent monomer or mixture thereof.     
     
     
       15. An article according to claim 14 in which said article is a tire and said coating is bonded to the inner surface of said tire. 
     
     
       16. An article according to claim 15 in which said tire is a tubeless tire. 
     
     
       17. An article according to claim 15 in which said coating is from about 0.001 to about 0.020 inch thick. 
     
     
       18. An article according to claim 14 wherein said coating is adhered to said substrate through a surface of said substrate which has been treated to improve adhesion of said coating, said article being prepared by treating a surface of an uncured rubber substrate in order to improve adhesion of a photocurable composition thereto, applying a photocurable composition to said surface, and both photocuring said photocurable composition and curing said substrate by application of heat and pressure. 
     
     
       19. An article according to claim 18 in which said coating is adhered to said substrate through an intermediate later between said surface of said substrate and said elastomeric coating, said intermediate layer comprising a photocured addition polymerizable monomer or mixture thereof. 
     
     
       20. An article according to claim 19 in which said treating a surface comprises applying a primer and a photocurable surface treatment composition containing an addition polymerizable reactive monomer or mixture thereof to said surface and irradiating said surface. 
     
     
       21. A process according to claim 4 wherein said actinic light is ultraviolet light. 
     
     
       22. A process according to claim 8 in which said treating of said surface includes application of an adhesion promoting material prior to applying said radiation curable composition, said adhesion promoting material being a material which promotes adhesion of said radiation curable composition to the uncured rubber substrate. 
     
     
       23. A process according to claim 6 in which said adhesion improving reactive monomer is isocyanatoethyl methacrylate. 
     
     
       24. A process according to claim 10 in which said addition polymerizable reactive monomer is an acrylate or methacrylate of a long chain alcohol or a mixture thereof. 
     
     
       25. An article according to claim 14 wherein said coating is a photocured reaction product and said photocurable composition further comprises a photoinitiator or mixture thereof. 
     
     
       26. A process according to claim 13 in which said polyurethane is an isocyanate terminated prepolymer end capped with a hydroxyalkyl acrylate or methacrylate and the elastomer coating has low air permeability. 
     
     
       27. An article according to claim 18 in which said photocurable composition further comprises a photoinitiator. 
     
     
       28. An article according to claim 27 in which said isocyanate terminated prepolymer is end capped with a hydroxyalkyl acrylate or methacrylate. 
     
     
       29. A process for preparing a tire having a low air permeability elastomer coating on the inner surface thereof, said process comprising: (a) treating the inner surface of said tire in order to improve adhesion of said elastomer coating to said tire;   (b) applying to the treated surface an elastomer-forming radiation curable composition comprising: (1) from about 60 to about 90 parts by weight of an end capped prepolymer having a molecular weight in the range of about 2,500 to about 10,000, said prepolymer being a reaction product of (i) a polyester diol having a molecular weight in the range of about 700 to about 1500, and formed by reaction of an alkanediol containing from 2 to about 6 carbon atoms with an aliphatic dicarboxylic acid containing from 2 to about 10 carbon atoms; (ii) an organic diisocyanate and (iii) an addition polymerizable end group compound having one carbon-to-carbon double bond and one hydroxyl group per molecule, wherein the mole ratio of --NCO groups is said diisocyanate to --OH groups in said diol is from about 1.12 to about 1.4, and wherein said end capped prepolymer is prepared by first reacting said polyester diol with said diisocyanate to form a diisocyanate terminated polyester urethane prepolymer comprising alternating units of said polyester diol and said diisocyanate and containing from about 2 to about 8 polyester diol units per mole, and then reacting said diisocyanate terminated prepolymer with said end group compound; and   (2) from about 40 to about 10 parts by weight of a monofunctional addition polymerizable reactive diluent monomer or mixture thereof; and     (c) radiation curing said radiation curable composition, whereby a cured elastomer coating having low air permeability is formed.   
     
     
       30. A tire comprising an elastomeric coating of low air permeability bonded to the inner surface thereof, said coating being a radiation cured reaction product of a composition comprising: (1) from about 60 to about 90 parts by weight of an end capped prepolymer having a molecular weight in the range of about 2,500 to about 10,000, said prepolymer being a reaction product of (i) a polyester diol having a molecular weight in the range of about 700 to about 1500, and formed by reaction of an alkanediol containing from 2 to about 6 carbon atoms with an aliphatic dicarboxylic acid containing from 2 to about 10 carbon atoms; (ii) an organic diisocyanate and (iii) an addition polymerizable end group compound having one carbon-to-carbon double bond and one hydroxyl group per molecule, wherein the mole ratio of --NCO groups is said diisocyanate to --OH groups in said diol is from about 1.12 to about 1.4, and wherein said end capped prepolymer is prepared by first reacting said polyester diol with said diisocyanate to form a diisocyanate terminated polyester urethane prepolymer comprising alternating units of said polyester diol and said diisocyanate and containing from about 2 to about 8 polyester diol units per mole, and then reacting said diisocyanate terminated prepolymer with said end group compound; and   (2) from about 40 to about 10 parts by weight of a monofunctional addition polymerizable reactive diluent monomer or mixture thereof.